1. Field of the Invention
The present invention relates to an optical imaging system for a copying machine that produces reduced sized images in one direction. More specifically, it relates to an optical imaging system that projects an image of an original moving relative to the optical system in the object space onto a light-sensitive element moving relative to the optical system in the image space, such that the speed of an image point in the image plane which corresponds to an original point is unequal to the speed of the light-sensitive element.
2. Description of the Prior Art
Optical imaging systems of the kind described above are generally known. For example, U.S. Pat. No. 4,394,083 discloses a copying machine with an imaging system having arrays of focusing lenses known as SELFOC. In the copying machine therein disclosed an original lying on a transparent plate, and a light-sensitive element disposed on a rotating drum, are taken along a lens array in directions perpendicular to the plane passing through the optical axes of the lenses. In order to image an original in reduced form in one direction, such as in the direction of travel, the speed at which the transparent plate is moved is increased.
A disadvantage of the copying machine disclosed in U.S. Pat. No. 4,394,083 is movement unsharpness which is an unsharpness in the image that occurs due to the increase in speed of the image on the light-sensitive element. For example, an image point of the original, as seen in the direction of travel, will be imaged as a line, the length of which increases with the distance over which imaging takes place. This distance is known as the slit width. According to U.S. Pat. No. 4,394,083, with a slit width above approximately 3 mm, the unsharpness due to the relative movement in the image would become such that the resulting copy would be unacceptable. There is, thus, a need to overcome this disadvantage of movement unsharpness.
U.K. Patent No. 2,122,362 discloses a copying machine of the 1:1 imaging of an original on a light-sensitive element, wherein both the original and the light-sensitive element form the same acute angle with the optical axis of the focusing array so as to correctly form an image of the original. Additionally, both are moved at the same speeds relative to the array. This British patent further indicates that if only the original or if only the light-sensitive element is at an acute angle with the optical axis, relatively unclear imaging occurs.
Similarly, U.S. Pat. No. 4,158,497, although disclosing a copying machine wherein the speed of the original is unequal to the speed of the photosensitive drum, provides that both the original and the photosensitive drum form the same acute angle with the optical system so as to correctly form an image of the original. The same unclear imaging that occurs in the device of U.K. Patent No. 2,122,362 occurs in this copying machine. Thus, neither U.K. Patent No. 2,122,362 or U.S. Pat. No. 4,158,497 overcome the disadvantage of movement unsharpness.